Actually fix issue #21484 reported by the customer. (#21850)
Actually fix issue #21484 reported by the customer. (#21850)

GC heap globals like ephemeral_heap_segment and finalize_queue are
null/invalid for a server GC. Add a check to skip the workstation GC
memory enumeration if server. The server memory enumeration already
skips if workstation GC.
wtgodbe/coreclr,poizan42/coreclr,wtgodbe/coreclr,cshung/coreclr,krk/coreclr,poizan42/coreclr,wtgodbe/coreclr,cshung/coreclr,wtgodbe/coreclr,cshung/coreclr,poizan42/coreclr,mmitche/coreclr,mmitche/coreclr,mmitche/coreclr,krk/coreclr,wtgodbe/coreclr,cshung/coreclr,mmitche/coreclr,wtgodbe/coreclr,cshung/coreclr,poizan42/coreclr,krk/coreclr,mmitche/coreclr,poizan42/coreclr,krk/coreclr,mmitche/coreclr,cshung/coreclr,poizan42/coreclr,krk/coreclr,krk/coreclr